AntDB 数据库采用复制组多副本架构，保证数据库的高可用性。同时，AntDB 支持单机、机房和城市级别的容灾，提供双中心部署方案。用户可根据机房配置和容灾需求，选择合适的方案进行部署。

本章所述的双中心集群结构如下：

主中心：一主两备

备中心：一主两备

两者关系：备中心的主是主中心主节点的异步备

主中心部署

参考【高可用集群模式部署】搭建一主两备高可用集群。

搭建完成，集群如下所示：

adbhamgrctl -c /etc/adbhamgr/adbhamgr_antdbcluster.yaml  list

+ Cluster: antdbcluster (7308609900027656685) ---+---------+----+-----------+
| Member     | Host               | Role         | State   | TL | Lag in MB |
+------------+--------------------+--------------+---------+----+-----------+
| adbhamgr-1 | 10.21.10.222:6655  | Leader       | running | 2  |           |
| adbhamgr-2 | 10.21.10.223:6655  | Sync Standby | running | 2  |         0 |
| adbhamgr-3 | 10.21.10.224:6655  | Replica      | running | 2  |         0 |
+------------+--------------------+--------------+---------+----+-----------+

备中心部署

一键式部署

参考【高可用集群模式部署】，搭建一主两备高可用集群，方法和搭建主中心一致。

例如，集群如下所示，此时主备中心是两个独立的集群。

adbhamgrctl -c /etc/adbhamgr/adbhamgr_antdbcluster.yaml  list

  + Cluster: antdbcluster (7234420149554224469) ---+---------+----+-----------+
  |  Member    | Host               | Role         | State   | TL | Lag in MB |
  +------------+--------------------+--------------+---------+----+-----------+
  | adbhamgr-1 | 10.1.206.202:55551 | Leader       | running |  2 |           |
  | adbhamgr-2 | 10.1.206.213:55551 | Sync Standby | running |  2 |         0 |
  | adbhamgr-3 | 10.1.206.226:55551 | Replica      | running |  2 |         0 |
  +------------+--------------------+--------------+---------+----+-----------+

停止备中心

停止 adbhamgr 服务（所有节点都要执行）：

sudo systemctl stop adbhamgr

使用 adbhamgr 的 remove 命令清理集群数据（一个节点执行即可）：

# remove后跟的参数“antdbcluster”为集群名称
[antdb@localhost ~]$ adbhamgrctl -c /etc/adbhamgr/adbhamgr_antdbcluster.yaml remove antdbcluster
+ Cluster: antdbcluster (7240007647780694395) -------+----+-----------+
| Member    | Host               | Role    | State   | TL | Lag in MB |
+-----------+--------------------+---------+---------+----+-----------+
| adbhamgr-3 | 10.1.206.226:55551 | Replica | stopped |    |   unknown |
+-----------+--------------------+---------+---------+----+-----------+
Please confirm the cluster name to remove: antdbcluster
You are about to remove all information in DCS for antdbcluster, please type: "Yes I am aware": Yes I am aware

重建备中心

步骤一：修改主中心的 hba 文件

重建备中心需要执行 adb_basebackup 命令，因此需要配置 hba，从而允许备机通过流复制连接到主节点。

1、修改主节点的 pg_hba.conf 文件，例如：

host    replication     all             0.0.0.0/0            trust

2、reload 主节点，使配置生效；

adb_ctl reload -D /home/antdb/data

步骤二：主中心的主节点创建复制槽（可选）

# 记录下创建的复制槽名称为adbhamgr（自定义）
select pg_create_physical_replication_slot('adbhamgr', true);

步骤三：重建备中心（每个节点都执行，操作一样）

下面以数据目录 /home/antdb/data/ 为例。

1、清理数据目录；

rm -rf /home/antdb/data/*

2、修改 adbhamgr 的配置文件；

# 备中心adbhamgr的yml配置文件中bootstrap.dcs下添加 standby_cluster 参数块，如下：
bootstrap:
  # this section will be written into adbdcs:/<namespace>/<scope>/config after initializing new cluster
  # and all other cluster members will use it as a `global configuration`
  dcs:
    ……
    standby_cluster:               # 添加standby_cluster参数设置，注意对其格式
      host: 10.21.10.222           # 主中心某个节点ip, 执行adb_basebackup和建立流复制的远程节点
      port: 6655                   # 远程节点的端口
      primart_slot_name: adbhamgr  # 建立流复制的复制槽，如果使用，需要手动在主中心建立相应的复制槽。（步骤二创建）
      create_replica_methods:      # 建立基础备份使用的方法，一般为adb_basebackup
        - basebackup

注意：host设置的节点与primart_slot_name所在的节点要保持一致。
     这里建议设置为主中心的主节点，与上述步骤一、二都是以主中心的主节点操作保持一致。

3、最后，启动各节点的 adbhamgr；

# 启动各节点的adbhamgr：
sudo systemctl start adbhamgr

# 成功后查看集群状态,备中心的主节点为Standby Leader，其余节点都是Replica
[antdb@localhost ~]$ adbhamgrctl -c /etc/adbhamgr/adbhamgr_antdbcluster.yaml list
+ Cluster: antdbcluster (7240007647780694395) ----+---------+----+-----------+
| Member    | Host               | Role           | State   | TL | Lag in MB |
+-----------+--------------------+----------------+---------+----+-----------+
| adbhamgr-1 | 10.1.206.202:55551 | Standby Leader | running |  5 |           |
| adbhamgr-2 | 10.1.206.213:55551 | Replica        | running |  5 |         0 |
| adbhamgr-3 | 10.1.206.226:55551 | Replica        | running |  5 |         0 |
+-----------+--------------------+----------------+---------+----+-----------+

# 查看备中心主节点的流复制，可以看到备中心的主节点的流复制源是主中心的主节点
[antdb@localhost ~]$ adb -d antdb -p 55551 -h 10.21.10.222
psql (13.3)
Type "help" for help.
antdb=# \x
Expanded display is on.
antdb=# select * from pg_stat_wal_receiver;
-[ RECORD 1 ]---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
pid                   | 3565881
status                | streaming
receive_start_lsn     | 0/8000000
receive_start_tli     | 5
written_lsn           | 0/8000148
flushed_lsn           | 0/8000000
received_tli          | 5
last_msg_send_time    | 2023-06-05 14:46:43.939936+08
last_msg_receipt_time | 2023-06-05 14:45:14.263009+08
latest_end_lsn        | 0/8000148
latest_end_time       | 2023-06-05 14:02:36.843889+08
slot_name             |
sender_host           | 10.21.10.211
sender_port           | 55551
conninfo              | user=replicator passfile=/data/antdb/.pgpass channel_binding=prefer dbname=replication host=10.21.10.211 port=55551 application_name=adbhamgr-1 fallback_application_name=antdbcluster sslmode=prefer sslcompression=0 ssl_min_protocol_version=TLSv1.2 gssencmode=prefer krbsrvname=postgres target_session_attrs=any


# 查看备中心备节点的流复制，可以看到备中心的备节点的流复制源是备中心的主节点
antdb=# select * from pg_stat_wal_receiver;
-[ RECORD 1 ]---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
pid                   | 866301
status                | streaming
receive_start_lsn     | 0/8000000
receive_start_tli     | 5
written_lsn           | 0/8000148
flushed_lsn           | 0/8000000
received_tli          | 5
last_msg_send_time    | 2023-06-05 14:46:38.010682+08
last_msg_receipt_time | 2023-06-05 14:46:37.350915+08
latest_end_lsn        | 0/8000148
latest_end_time       | 2023-06-05 14:01:34.527452+08
slot_name             | adbhamgr_2
sender_host           | 10.1.206.202
sender_port           | 55551
conninfo              | user=replicator passfile=/data/antdb/.pgpass channel_binding=prefer dbname=replication host=10.1.206.202 port=55551 application_name=adbhamgr-2 fallback_application_name=antdbcluster sslmode=prefer sslcompression=0 ssl_min_protocol_version=TLSv1.2 gssencmode=prefer krbsrvname=postgres target_session_attrs=any

e=adbhamgr-2 fallback_application_name=antdbcluster sslmode=prefer sslcompression=0 ssl_min_protocol_version=TLSv1.2 gssencmode=prefer krbsrvname=postgres target_session_attrs=any